Recovery system of waste heat from flue gas

Abstract

A recovery system of waste heat from flue gas. The system includes a first heat exchanger and a second exchanger. The first heat exchanger includes a heat absorption section, a heat release section, and a first pipeline. The second heat exchanger includes a second pipeline including an inlet header and an outlet header. The system further includes a third pipeline. The first heat exchanger is disposed at a relatively high temperature side of a flue, the second heat exchanger is disposed at a relatively low temperature side of the flue, and the first heat exchanger and the second heat exchanger are connected by the third pipeline. The heat absorption section and the heat release section are connected by the first pipeline to form a circulation loop; the heat absorption section is disposed in the flue; the heat release section is disposed in the third pipeline.

The invention claimed is: 
     
       1. A recovery system of waste heat from flue gas, the system comprising:
 a) a first heat exchanger, the first heat exchanger comprising a heat absorption section, a heat release section, and a first pipeline; 
 b) a second exchanger, the second heat exchanger comprising a second pipeline comprising an inlet header and an outlet header; and 
 c) a third pipeline; 
 
       wherein
 the first heat exchanger is disposed at a relatively high temperature side of a flue, the second heat exchanger is disposed at a relatively low temperature side of the flue, and the first heat exchanger and the second heat exchanger are connected by the third pipeline; 
 the heat absorption section and the heat release section are connected by the first pipeline to form a circulation loop; the heat absorption section is disposed in the flue; the heat release section is disposed in the third pipeline; and 
 when in use, a medium to be heated is introduced to the second exchanger along the third pipeline and the inlet header in sequence for heat exchange, and flows out from the outlet heater of the second exchanger. 
 
     
     
       2. The system of  claim 1 , wherein the third pipeline comprises a first branch and a second branch which are connected in parallel; the heat release section of the first heat exchanger is disposed in the first branch; and the second branch is configured to regulate a flow rate of the medium. 
     
     
       3. The system of  claim 2 , wherein a regulating valve is disposed on the second branch of the third pipeline, and the regulating valve is controlled by a control device. 
     
     
       4. The system of  claim 3 , wherein a temperature measuring point is disposed on the first pipeline connecting the heat absorption section and the heat release section, and the temperature measuring point transmits a temperature signal to the control device. 
     
     
       5. The system of  claim 4 , wherein tube bundles of the second heat exchanger contacting with flue gas comprises plain carbon steel. 
     
     
       6. The system of  claim 1 , wherein when in use, the first pipeline of the first heat exchanger is filled with forced circulating water. 
     
     
       7. The system of  claim 1 , wherein when in use, the medium to be heated is low temperature feedwater supplied for a boiler. 
     
     
       8. The system of  claim 1 , wherein tube bundles of the second heat exchanger contacting with flue gas comprises corrosion resisting steel. 
     
     
       9. The system of  claim 1 , wherein tube bundles of the second heat exchanger contacting with flue gas comprises plain carbon steel.